<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<select id="s1" onchange="onch()">
			<option value ="">请选择</option>
			<option value ="https://www.baidu.com/">百度</option>
			<option value ="https://www.4399.com/">4399</option>
			<option value ="https://www.7k7k.com/">7k7k</option>
		</select>
	</body>
	<script type="text/javascript">
		function onch(){
			var url = document.getElementById('s1').value;
			location.href = url;
		}
	</script>
</html>